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Byssochlamys Rot in the Orchard and the Effectiveness of Fungicides against this New Disease

Megan Biango-Daniels: Cornell University

<div><em>Byssochlamys nivea</em> is an important heat-resistant spoilage mold that produces the mycotoxin, patulin. Recent work demonstrates that this species is also a post-harvest pathogen of apples, however the point of infection remains unknown. Latent infection of apples by <em>B. nivea</em> in the field may lead to storage and shelf spoilage. To test the hypothesis that <em>B. nivea </em>can infect apples in the orchard, a field trial was conducted on ‘Gala’ apples that were inoculated or mock-inoculated with <em>B. nivea</em>. The resulting pre-harvest symptoms were compared to symptoms of Byssochlamys rot under post-harvest conditions. The sensitivity of <em>B. nivea</em> to post-harvest fungicides labeled for apples (difenoconazole, fludioxonil, or pyrimethanil) was also determined for 30 <em>B. nivea</em> isolates. We found that <em>B. nivea</em> can infect apples through wounds in the orchard, leading to symptoms like those observed post-harvest. For all fungicides tested, percent relative growth (dose of EC<sub>50</sub> and 10x EC<sub>50</sub>) of <em>B. nivea</em> isolates from agricultural environments was higher than those from non-agricultural environments. Controlling Byssochlamys rot with fungicides may be complicated by selection for fungicide resistance.</div>